UC Santa Cruz

Telomeres are nucleoprotein structures that protect the ends of linear chromosomes. Telomeres serve two functions within the cell: to protect against genetic loss due to chromosomal shortening as a result of the end replication problem, and to distinguish chromosomal termini from sites of DNA damage that would otherwise elicit an unwanted DNA damage response. The foundation of telomere structures begins with a hexameric double-stranded repeat DNA sequence (TTAGGG in vertebrates) ranging from 2-20kb in length and terminate in a 3’ G-rich single-stranded DNA overhang ranging from 50-300bp in length. Telomeric chromatin is known to contain tightly spaced nucleosomes, as well as a telomere-specific protein complex known as the shelterin complex. It is known that the shelterin complex is responsible for providing telomere end protection, however the mechanistic details of how this complex establishes end protection is lacking. Furthermore, how this complex transitions the telomere from a protected state required for end protection into an open deprotected state required for telomere replication remains largely unknown. This thesis outlines single-molecule studies of both telomeric DNA and telomere-interacting proteins to further our understanding of how these structures protect the genome.